The book provides a compelling and comprehensive explanation of the puzzling resilience of the gangs that have operated in Rio de Janeiro since the 1980s. It offers a broad overview of the history of gangs and gang alliances (factions) in the whole of the city, focussing on the evolution and consistency of these groups over time, positing the link between these and the groups’ chances of survival. It draws on more than 285 articles from 15 newspapers and media outlets across a time span covering more than 40 years, supplemented with interviews with high-ranking public security officers and secondary data. Applying a novel and composite translation of biological evolutionary concepts to a complex criminological context, it focusses on three main fields of interest: territory, relations, and internal dynamics.